Crystal structure, defect relaxation, and microwave dielectric properties of Ba[(Mg1/3Nb2/3)1−xHfx]O3 solid solutions

Abstract

AbstractBa[(Mg1/3Nb2/3)1−xHfx]O3 (BMNH, x = 0.05, 0.1, 0.15, 0.2) solid solutions were prepared via the solid‐state reaction method. The effect of BaHfO3 on the crystal structure, microwave dielectric performance, and defect relaxation behavior of Ba(Mg1/3Nb2/3)O3 (BMN) were studied. BaHfO3 additions degraded the sintering activity of BMN powder, requiring a high sintering temperature (Ts) ~ 1650°C; but it could be effectively improved by a prolonged sintering process at a lower Ts of 1600°C. The well‐sintered BMNH ceramics (1600°C for 30 h) possessed a high densification >96%, and exhibited cubic perovskite structures without 1:2 cation ordering. Once doped with Hf, the low‐temperature relaxation in dielectric spectroscopy and thermally stimulated depolarization current (TSDC) for pure BMN disappeared, further indicating such relaxation is related to cation‐ordered structure. Oxygen vacancies, namely showing in‐grain and across‐grain‐boundary relaxation of ‐related defects, were the main defect types in BMNH. The concentrations of in‐grain decreased as x increased, which is beneficial to BMNH to maintain high Q × f values of 69 400‐73 000 GHz. Accompanied by a high εr of 33.27‐33.59 and a low τf of +13.6 to +20.7 ppm/°C, these materials have a good potential for applications in microwave components and devices.